Addition products of bisulphites and prepolymers containing isocyanate groups and the use of aqueous solutions of such adducts for the shrinkproof and feltproof finishing of keratin-containing textiles have been disclosed, for example, in German Offenlegungsschrift No. 2,307,563 (similar to U.S. Pat. No. 3,898,197) and German Auslegeschrift No. 2,414,470 (similar to U.S. Pat. No. 3,984,365). In the known processes, the textile material is impregnated with a relatively concentrated solution of the bisulphite adduct (e.g. by immersion, spraying or brush coating) and then freed from excess impregnating substance by squeezing. The process has the disadvantage that may manufacturers lack the necessary machinery. Moreover, certain textile materials, e.g. flannel-finished knitted goods based on keratin-containing fibers, can only be treated in long baths. There is, therefore, a need for a process by which the keratin-containing textile can be treated with the above-mentioned bisulphite adducts in a long aqueous bath.
In practice, however, it is found that it is not so easily possible to apply bisulphite adducts of polyisocyanates to textiles by a process of absorption from a long bath. The reason for this is that the bisulphite adducts are only slowly and incompletely absorbed on the textile material from dilute aqueous solutions. This applies particularly to the slightly alkaline baths which are used in practice in order to accelerate the cross-linking reaction of the bisulphite adduct during the subsequent heat treatments of the textile. While U.S. Pat. No. 3,898,197 does refer to exhaustion of bisulphite adducts from acidic long aqueous baths, it does not suggest pretreating the substrate.
It has now been found that textile materials based on keratin-containing fibers can be given a felt-free finish by a process of absorption from long baths of aqueous solutions of polyisocyanate/bisulphite addition products if the textile is first pretreated with a long aqueous bath containing relatively high molecular weight compounds having cationic groups and organic salts of polyvalent metals such as calcium, magnesium, zirconium, zinc, aluminum or chromium.
The aqueous liquors preferably contain calcium chloride and magnesium chloride in addition to the compounds having cationic groups.
The term "long baths" used in the present invention means that the proportion by weight of the textile material which is required to be treated to the aqueous treatment bath is greater than about 1:8 and preferably in the range of from about 1:10 to 1:60, most preferably from about 1:20 to 1:40.
A process for creaseproofing textiles in which the textile materials are impregnated with solutions or dispersions of isocyanate prepolymers, dried and finally treated with solutions or emulsions of surface-active agents has been disclosed in German Offenlegungsschrift No. 1,619,021 (similar in disclosure to British Pat. No. 1,131,006). Although bisulphite adducts of isocyanate prepolymers are also mentioned as impregnating agents in this process and the compounds which may be used as surface-active agents according to German Offenlegungsschrift No. 1,619,021 also include compounds having cationic groups, the effect of more rapid and more complete absorption of the bisulphite adduct on the keratin-containing textile, which is the basis of the present invention, is not achieved in the process according to German Offenlegungsschrift No. 1,619,021, in which the surface-active agent is only subsequently applied to the textile.
In Australian Patent Application 68419/74, which is a prior publication, cationic compounds are described for the preliminary treatment of keratin-containing textiles to enable them to absorb polyisocyanate/bisulphite addition products. The felt-free effects obtained by this process are, however, very uneven and vary according to the type of textile material and the dye. Thus, for example, satisfactory feltproof effects cannot be obtained by this process if the keratin-containing textile has been dyed with after-chroming dyes or reactive dyes.
There are other processes used in practice in which the polyisocyanate/bisulphite addition product is used together with metal salts, preferably magnesium chloride. The aqueous liquor is in these cases made alkaline, e.g. using ammonia. These processes have the disadvantages of the formation of deposits and precipitates in the treatment bath which cause the formation of patches in the textile material and the accumulation of deposits in the treatment apparatus. Furthermore, the feltproof effects obtained by these processes are unsatisfactory, especially on textiles which have been dyed with after-chroming dyes.